Known in the related art is a ball joint that includes a ball stud with a spherical ball section and a shaft-shaped shaft section and a holder that rotatably holds the ball section. For example, Patent Literature 1 described below discloses a ball joint, of which a ball head portion is formed by inserting a male screw section, a screw shaft-shaped member, into a mold for molding a ball head corresponding to a shape of a spherical ball head portion to inject dissolved resin and connected to the screw shaft-shaped member, and a method for manufacturing the ball joint.